Structure and Properties of Matter

The atom is largely empty space with electrons moving about. Within the center of the atom is the atomic nucleus. The nucleus is tiny and has very high density. Surrounding the nucleus are the electrons. This electron cloud (an informal term) constitutes most of the volume of the atom.

Electrons- negatively charged and with a tiny small mass. Moves around the nucleus in electron shells

Electron Shells- this is the region of space around the nucleus. An atom can have up to 7 shells called K, L, M, N, O, P, and Q. Each shell holds up to a certain number f electrons, 2, 8, 18, 32 are the first four shells. The further away the shell is from the nucleus, the higher the energy of its electrons. If the very last shell, called outer shell, is full or has 8 electrons (octet), then the atom is stable.

Each shell consists of orbital, or probability clouds. The positions of electrons cannot be exactly determined at any one time.

Mass Number (A)- this is the number of protons and neutrons in the nucleus.

Atomic Number (Z)- this is the number of protons, in a nucleus.

Atomic Number (N)- Number of neutrons calculated by subtracting the atomic number from the mass number.

Atomic Weight- total number of particles in an atom's nucleus.

b. Know that isotopes of any element have different numbers of neutrons but the same number of protons, and that some isotopes are radioactive

Isotopes- Atoms with differing number of neutrons will affect the mass number (protons and neutrons). Thus, different isotopes of a given element will have different mass number. Different isotopes with different number of neutrons have the same chemical properties.

To find the number of protons, neutrons, and electrons in an isotope: First- find the atomic number of the element and mass number (sum of protons and neutrons) of the isotope. The mass number is usually written right after the name of the element. Second- to find the number of protons-- the atomic number is the number of protons in an element. Third- to find the number of electrons-- if the atom has a neutral charge, then you must have an equal number of protons and electrons. If the atom has a negative charge, then you will have more electrons than protons. An atom with a positive charge will have fewer electrons than protons. Protons- total charge=electrons.Fourth- to find the number of neutrons-- take the mass number and subtract the number of protons to find the neutrons.

Practice: The isotopes Carbon 12 and Carbon 14 are both isotopes of Carbon (atomic number 6). Carbon 12 Number of protons is its atomic number, so it has 6 protonsNumber of electrons is the same as protons, so it has 6 electronsNumber of neutrons--> mass number - protons=> 12-6=6, 6 neutrons

Carbon 14 Number of protons is 6Number of electrons is 6Number of neutrons is 8 (14-6)

Practice: Find the number of protons, electrons and neutrons in Neon 20 (Neon has an atomic number of 10 and atomic mass of 20).Protons= Neutrons=Electrons=

Isotopes that are Radioactive- Most naturally occurring atomic nuclei are stable and remain intact indefinitely. Others are not stable and spontaneously emit rays, radiation, and particles (I.e., alpha). As radiation of particles are emitted, unstable radioactive elements will transform into a stable one.

Atoms- these are the smallest particle that represents an element. Smallest part of a substance that exists and retains the properties of a substance.

Elements- an element is a substance that cannot be broken down through chemical reactions. There are over 100 known elements. Most are solids or gases at room temperature.

Molecules- a single particle composed of nonmetal atoms. Held together by covalent bonds and share valence electrons. For examples, water is composed of hydrogen gas and oxygen gas. (If a metal is attracted to a nonmetal, they are called Ionics and are held together through ionic bonding. They have strong bonds, and thus have high melting point in order to break the bonds. Able to conduct electricity.)

Compounds- two or more elements bonded together. A compound has different physical and chemical property from the element it is made out of. Compounds are difficult to split and can only be taken apart into their elements through chemical reactions or electrolysis. Binary compounds are composed of two elements only. For example, CO (carbon monoxide) is made up of only carbon and oxygen.

Mixture- a blend of two or more elements and or compounds in which each substance retains its own chemical identity and properties. A mixture can usually be separated into its elements or compounds through physical means.

d. Compare and contrast states of matter and describe the role energy plays in the conversion from one state to another

Matter- a substance that has mass and occupies volume. Matter exists as either a liquid, solid, gas, or plasma.

Solid- a substance in a solid state that has a fixed, definite volume. The particles in a solid are packed tightly together. This holds the substance in rigid position and cannot be compressed. Has fixed state.

Liquid- a substance in liquid state has particles that are loosely packed together. The substance has a variable shape and takes the shape of its container. Its volume is fixed and can be compressed slightly.

Gas- a gaseous substance has particles that are widely spread apart thus it has no shape. Its volume is not fixed. As its volume increases, the gas expands and particles move farther away from each other. As its volume decreases, the gas compresses and move closer to each other. Can be compressed significantly.

Plasma- hot gas-like state composed of the ions and electrons that can carry out electrical current.

Kinetic Theory- states the behavior of different states of matter in terms of energy (the motion of molecules)

Solid- particles are close together because they have the least amount of energy. Intermolecular force is strong, thus it is able to hold and lock molecules in place.

Liquid- particles are further apart because they have more energy than solids do. The attractive forces, however, are not strong enough to prevent gliding among molecules.

Gas- particles are the furthest apart with the most energy. Overall, gases have a weaker strong attractive force between molecules which allows gas to expand.

Substances can exist as a solid, liquid, or gas by changing the energy (temperature). Solids can be changed in a liquid by increaseing the temperature. As temperature increases, the particles energy increases, thus allowing more movement and spreading apart. This process is called melting. Increasing temperature even more causes energy to increase more movement of particles, and further aprt into a gaseous state, called vaporizing. Vice versa, by decreasing temperature, energy drops, movement drops, and condense back into a liquid. Further decreasing temperature, decreases movement, and energy undergoes freeing in a solid. Can have direct change of state from gas to solid called deposition and solid to gas called sublimation.

Boiling point- this refers to the energy that is required to break the bonds between the molecules. Once the bonds are broken, molecules can separate and form vapor. More energy is required to break very strong attractive forces.

Melting point- similar to boiling point, the stronger the attractive forces between the molecules, the higher the temperature for melting point.

Hardness- the resistance to permanent deformation

Color- determined by the particular wavelengths a substance absorbs and reflects.

Density- the density of an object depends on the mass and volume.

Conductivity- two types, electrical and thermal

Electrical- this is the ability of a substance to allow for the flow of current

Thermal- this is the ability of a substance to conduct heat; based on the intensive property, which means that it doesn't matter how much substance there is, it will conduce the same amount of heat

f. Recognize that all chemical substances are characterized by a unique set of physical properties

Chemical property- the chemical property of a substance describes its chemical reaction with other substances. You can use the periodic table to predict chemical behavior. The periodic table is arranged according to families of elements and in general give similar reactions.

g. Define and calculate density, and predict whether an object will sink or float in a fluid

To find the Density of a material: mass divided by its volume (think DMV)D=M/V

Water is 1g/mL (1 g/cm3). If the density of an object is less than 1g/cm3, it will sink into the water until it displaced an amount of water equal to its own mass. Thus, a 1 g object will sink until it displaces 1 g of water. If an object is placed in a bin of water, it will float if its density is less than 1g/mL. If an object's density is greater, then it will sink.

For example, will a box float if each side is 5 cm and has a mass of 250 grams? Scroll down to find the answer

Answer: No, it's density is 2 g/cm3, thus it will sink.

h. Explain that chemical changes in materials result in the formation of a new substance corresponding to the rearrangement of the atoms in molecules

In a chemical change, the chemical composition does not stay the same. For example, if you drop an antacid into a cup of water, the chemical composition is not the same after the change. The total number of atoms involved in a chemical reaction stays the same (none are reduced or increased).

For a chemical change to occur, the chemical bonds must be altered. Valence electrons are involved in the formation or breaking of bonds.

I. Explain and apply principals of conservation of matter to chemical reactions, including balancing chemical equations

The law of conversation states that mass is neither created nor destroyed by chemical reactions or physical changes. Thus, according to the law of conservation of mass, the mass of the products in a chemical reaction must be the same as the mass of the reactants. We use chemical equations to represent the chemical reaction that took place. Each side of the equation must have the same number of atoms; the equation must be balanced.

Practice: Balance this equationH2 + O2 --> H2O

The equation is unbalanced as there is an unequal amount of atoms on each side of the equation. On the left side and on the right we have 2 Hydrogen atomsOn the left side we have 2 oxygen atoms and on the right we have one

So, why the hydrogens are in balance, the oxygens are not. We can put a 2 in front of the water on the right sideH2 + O2 ---> 2H2O

This now balances the oxygen atoms. 2 oxygens on the left side and 2 on the right. However, this now caused the hydrogens to become unbalanced. To balance it, we can place a 2 in front of the H2 on the left side.

2H2 + O2 ---> 2H2O

The equation is now balanced.

Some notes when balancing an equation: 1) You cannot change the subscript2) You cannot place a coefficient in the middle of a formula

Practice:Balance the following equation (scroll down for the answer)H2 + Cl2 ---> HCl

Answer:H2 + Cl2 ---> 2HCl

Practice: O2 -----> O3

Answer: 3O2---> 2O3Think about the LCM to help balance this equation. The LCM of 2 and 3 is 6. This tells us how many atoms will be needed to balance the equation.

j. Distinguish among acidic, basic, and neutral solutions by their observable properties

Acid and base properties were proposed by Robert Boyle in 1661.

Acid- any substance that releases Hydrogen ions, H+ properties of an acidic solution

acids taste sour

litmus paper turns red in the presence of hydrogen ions

pH value is 7 or less

reacts with bases to give a salt and water

releases H+ when dissolved in water

called protons donors

Basic- any substance that releases hydroxide ions, OH-, in water.

bases taste bitter

bases feel slippery/soapy

litmus paper turns blue

pH value is greater than 7

reacts with acids to give salt and water

accepts/reacts with H+ ions

Acid-base indicators exhibits different colors due to a substance that is sensitive to a change in pH.

Salts- forms as a result of a chemical reaction between an acid and base. Example: NH3 + HCl --> NH4Cl. Another common example is HCl + NaOH --> H20 + NaCl. Do you recognize this equation? It is formed from the acid-base reaction of hydrochloric acid and sodium hydroxide- known as sodium chloride, the most common table salt. Another example: Ca + Cl2 --> CaCl2

H.G.J. Moseley bombarded atomic nuclei with high energy radiation. He discovered through this experiments that nuclear charge increases by 1 for each element. Thus, the periodic law states that the properties of elements recur in a repeating pattern when arranged according to increasing atomic number.

The arrangement of the elements starts on the left of period with hydrogen and moves in order of increasing atomic number. Each successive element has one more electron in the outer shell.

Group- vertical column in the periodic table, 18 columns, all are named except for transition metal. Have same number of electrons in outer shell. Elements in the same group have similar chemical properties. Groups of elements can be referred to by their family name:

outer shells are full, thus they are extremely stable, tend to not form chemical bonds, small tendency to gain or lost electrons

weak interatomic forces and thus low boiling and melting points

gases are odorless, colorless, and nonflammable

Period- horizontal row, 7 rows

1st Period- has two elements Hydrogen and Helium

2nd and 3rd Period- each have 8 elements (called short periods)

4th and 5th Period- have 18 elements (called long periods)

Representative Transition Group- chemical behavior is predictable, found in the A groups on the left and right side of the periodic table.

Transition elements- B groups in the middle of the table, chemical behavior is not as predicable

Inner-Transition elements- found in the main portion of the periodic table. Placed below table in order to avoid unduly wide periodic table.

Lanthanide Series- Ce through Lu, these have similar properties and are found in abundance in nature. Also referred as rare earth elements.

Actinide Series- All are radioactive and none of the elements after uranium is naturally occurring

As we move up a group of elements from bottom to top, the radii of the atom decreases because there are fewer energy levels of electrons surrounding the nucleus. Thus, the trend in atomic radius decreases up a group. As we move left to right within a period the radii of the atoms decrease. Because the number of protons increase as we move left to right, the nuclear charge of the elements increases which increases the pulling of electrons closer to the nucleus thus reducing the size of the atom.

The unusual shape of the table is the result of the ordering of energy sublevels. The order of energy sublevels follow the systematic arrangement of the elements by groups. Left area is called S block of elements. Right area are called p blocks. Transition area makeup of the d blocks. Inner transition comprise of the f block.

Number of sublevels corresponds to the number of main energy level. 1s<2s<2p<3s<3p<4s<3d<4p<5s<4d<5p<6s......

When an atom undergoes a chemical reaction, only the outermost electrons are involved, called valence electrons. They form chemical bonds between atoms and affect chemical behavior of the element. Predicting the number of electrons by looking at the group number in the periodic table (only works for representative elements). Group number is identical to the total number of valence electrons for example in group 1A, they all have 1 valence electrons. Group 5A has 5. Group 13 has three (look at the last digit).

l. Based on position in the periodic table, predict which elements have characteristics of metals, semimetals, nonmetals, and inert gases

Metals- elements on the left side of the periodic table have metallic properties. As you move to the right, the elements become less metallic. Groups 1-12 plus Al, Ga, In, Ti, Sn, Pb, Bi are metals. Metals are solid at room temperature (except for mercury), malleable, ductile, good conductors of electricity as well as heat, and shiny.

Semimetals- elements not distinctly metal or nonmetal, but have a mixture of properties. B, Si, Ge, As, Sb, Te, Po, At are al nonmetals. These elements separates metals and nonmetals, form steps down the periodic table.

Nonmetals- elements on the right of the periodic table. They are poor conductors of heat, can be at different phases at room temperature.

Inert gases- more commonly known as noble gases, group 18, unreactive under normal conditions

m. Explain chemical reactivity using position on the periodic table

Elements with in the same group have the same chemical properties and the same number of valence electrons.

n. Predict and explain chemical bonding using elements' position in the periodic table

Valence electrons- are found in the outer regions of an atom. They are found in the most distant s and p energy subshell. These electrons are responsible for holding two or more atoms together in a chemical bond.

According to the octet rule, atoms tend to bond in such a way that it acquires 8 electrons in its outer shell. This can occur by transfer of electrons from 1 atom to another, by sharing.

Ionic bond- occurs when a metal cation is attracted to a nonmetal anion. These are held together by the attraction by opposite charge. Fundamental particles held together by ionic bond is called formula unit.

Covalent bond- two non-metals share valence electrons. A fundamental particle held together by covalent bonds is a molecules. When a metal atom loses it valence electrons, it becomes positive charge forming a cation. So, if Na, n group 1 loses an electrons, it because Na_ and only has 10 electrons, the same as Ne (a noble gas). We call this isoelectronic, when main group metals achieve a noble gas electron configuration after losing one ore more electrons.

Anions are achieved when a nonmetal gains valence electrons and thus becomes negatively charged. For example, when Cl atom gains one valence electron (group 18), it becomes Cl0 and now has 19 electrons, the same as Ar. Because the cation loses an electrons, its radius becomes smaller because there is not more pull from the nucleus. Anions becomes larger between they gain an electrons because there is now less pull towards the nucleus.

Covalent- the electrons from the nonmetals belong to both and are shared to produce an octet to complete its valence shell. Since the valence shell is filled, the bond is stable. For example, in Hcl, the hydrogen atoms shares its one valence electron with the Cl atom. This gives Cl 8 electrons it its outer valance shell, thus making it isoelectronic with Ar and is stable. And Al shares one of its valence electrons with Hydrogen, giving it now 2 electrons in its outer shell. Hydrogen becomes isoelectronic with He. So both elements become stable.

Organic Compounds- contains the element carbon. Most organic compounds also contains hydrogen. Organic compounds can be found in nature, produced by living things, or synthesized in a laboratory. Organic compounds, because of their covalent bondings, are insoluble in water. When a carbon molecule is bonded with other carbon molecules, it can form many different kinds of molecules. Example of carbon compounds:

Organic and inorganic compounds work together efficiently in biological systems.

p. Explain the central role of carbon in living system chemistry

Currently around 10 million organic compounds account for about 90% of all known substances with over 50,000 new organic compounds being synthesized each year. One of the main reasons for their begin so many different organic compounds is because carbon atoms have the ability to link together to form long chains. Carbon is able to make large molecules with multiple bonds. Carbon is the central role in living systems because all living things are made of carbon, along with other elements. Carbon has four valence electrons so it can combine with large number of other elements. Carbon shares its valence electrons to form covalent bonds.